package class03;

import com.sun.javafx.logging.PulseLogger;

/**
 * @author zhangchaoliang
 * create 2022
 */
public class MergeSort {

    public static void mergeSort1(int[] arr) {
        if (arr == null || arr.length < 2) {
            return;
        }
        process(arr, 0, arr.length - 1);
    }

    public static void process(int[] arr, int L, int R) {
        if (L==R){
            return;
        }
        int mid = L+((R-L)>>1);
        process(arr,L,mid);
        process(arr,mid+1,R);
        merge(arr,L,mid,R);
    }

    public static void merge(int[] arr, int L, int M, int R) {
        int[] help = new int[R-L+1];
        int i=0;
        int p1=L;
        int p2=M+1;
        while (p1<=M&&p2<=R){
            help[i++]=arr[p1]<=arr[p2]?arr[p1++]:arr[p2++];
        }
        while (p1<=M)
            help[i++]=arr[p1++];
        while (p2<=M)
            help[i++]=arr[p2++];
        for (i=0;i<help.length;i++){
            arr[L+i]=help[i];
        }
    }


    public static void mergeSort2(int[] arr){
        if (arr==null||arr.length<2)
            return;
        int N =arr.length;
        int mergeSize = 1;
        while (mergeSize<N){
            int L=0;
            while (L<N){
                int M=L+mergeSize-1;
                if (M>N)
                    break;
                int R = M+Math.min(M+mergeSize,N-1);
                merge(arr,L,M,R);
                L=R+1;
            }
            if (mergeSize>N/2)
                break;
            mergeSize<<=1;
        }
    }

    public static int[] generateRandomArray(int maxSize,int maxValue){
        int[] arr = new int[(int)((maxSize+1)*Math.random())];
        for (int i=0;i<arr.length;i++){
            arr[i]=(int)((maxValue+1)*Math.random())-(int)((maxValue+1)*Math.random());
        }
        return arr;
    }

    public static int[] copyArray(int[] arr){
        if (arr==null){
            return null;
        }
        int[] res = new int[arr.length];
        for (int i=0;i<arr.length;i++){
            res[i]=arr[i];
        }
        return res;
    }

    public static boolean isEqual(int[] arr1,int[] arr2){
        if ((arr1==null&&arr2!=null)||(arr1!=null&&arr2==null)){
            return false;
        }
        if (arr1==null&&arr2==null){
            return true;
        }
        if (arr1.length!=arr2.length){
            return false;
        }
        for (int i=0;i<arr1.length;i++){
            if (arr1[i]!=arr2[i]){
                return false;
            }
        }
        return true;
    }

    public static void printArray(int[] arr){
        if (arr==null){
            return;
        }
        for (int i=0;i<arr.length;i++){
            System.out.println(arr[i]+" ");
        }
        System.out.println();
    }

    public static void main(String[] args) {
        int testTime = 500000;
        int maxSize = 100;
        int maxValue = 100;
        System.out.println("test begin!");
        for (int i=0;i<testTime;i++){
            int[] arr1 = generateRandomArray(maxSize,maxValue);
            int[] arr2 = copyArray(arr1);
            mergeSort1(arr1);
            mergeSort2(arr2);
            if (!isEqual(arr1,arr2)){
                System.out.println("Oops");
                printArray(arr1);
                printArray(arr2);
                break;
            }
        }
        System.out.println("test end!");
    }
}
